Method of producing glass materials from ash-slag waste

ABSTRACT

A method of obtaining glass materials from ash-slag. Waste wherein the waste is heated to a melting point temperature and melted in a reducing medium. The obtained melt is cooled by a thermal shock to form a foamed glass material. Prior to heating the charge, the carbon content therein is brought to 3.0-8.0 wt %, and the foamed glass material is foamed under a flow of a gaseous medium resulting form decomposition of carbides formed in the melt as a result of carbon content adjustment. Carbon addition also reduces iron oxide present in the waste, this reduction facilitating iron separation from the foamed material.

This is a continuation-in-part of Ser. No. 08/144,476 filed Nov. 2, 1993abandoned.

FIELD OF THE INVENTION

The present invention relates to construction materials, and,particularly, to a method of producing glass materials from ash-slagwaste which can also find wide application in chemical industry, inradio electronics and other branches of industry.

BACKGROUND OF THE INVENTION

Known in the art is a method of producing glass materials consisting inthat a charge including the following ingredients (wt %): 47.6 SiO₂,29.6 Al₂ O₃, 15.8 Fe₂ O₃, 4.2 CaO, 0.6 MgO, 1.7 K₂ O, 0.5 Na₂ O isheated to a melting point temperature and melted in a graphite crucible,whereupon the melt obtained is slowly cooled (E. J. Deguire, S. H.Risbud. Journal of Materials Science, v. 19, N6 (1984) 1760-1766"Crystallization and properties of glasses prepared from Illinois coalfly ash.")

The known method given a non-transparent material with a large contentof iron (15 wt %) which substantially reduces the field of itsapplication, particularly, makes it applicable only in constructionindustry and quite inapplicable in optical devices.

Known in the art is a method of preparation of glass materials fromash-slag waste having the following composition wt %:

    ______________________________________                                        CaO total       5.0-41.0                                                      CaO unbound     4.0-13.0                                                      SiO.sub.2      13.0-75.0                                                      Al.sub.2 O.sub.3                                                                              5.0-26.0                                                      carbon         1.0-2.0                                                        Fe.sub.2 O.sub.3                                                                              1-24                                                          MgO            2.0-6.0                                                        Na.sub.2 O     0.1-1.0                                                        K.sub.2 O      0.2-1.0                                                        SO.sub.3       0.1-0.6                                                        TiO.sub.2      0.2                                                            ______________________________________                                    

This ash-slag waste is the by-product of energy production using hardcoal and brown coal.

In this method, a charge of this ash-slag waste is heated to a meltingpoint in a reducing medium, whereupon the obtained melt is cooled by athermal shock till a glass material is formed (Reprint of the Instituteof physics of Siberian Division of the Academy of Sciences of the USSR,N 74, 1991 Krasnoyarsk, Pavlov V. F. et al. "A technique of Processingashes, coals KATEK") herein incorporated by reference.

This type of ash-slag waste is difficult to reprocess due to its highcalcium oxide content and presence of transient metals such as iron,manganese, chromium, titanium and others. The transient metals alsolimit the use of this waste material as a raw material for achievingtransparent glass ceramic materials.

In the prior art, glass materials from all known ash-slag wastematerials featuring comparatively low conductivity are used asheat-insulating materials. However, prior art methods fail to attaincomplete purification of the ash-slag waste being processed fromimpurities of transition metals, which to a great extent reduces therange of application of the glass materials since they can not beutilized in the manufacture of optically transparent glass materials.

As such, a need has developed to provide improved methods to obtainglass materials which are used for both for heat insulating applicationsand optical material applications. Responsive to this need, the presentinvention provides an improved method which overcomes the deficienciesin the prior art methods by the elimination of transient metalimpurities and bonding of calcium oxide to form a glass material usefulfor insulating, wear resistance and optical material application.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a method ofproducing glass materials from ash-slag waste, which will considerablyimprove the quality of the glass materials obtained due to completepurification of the charge from admixtures of transition metals andbinding of free calcium oxide.

One object of the present invention is to provide a method of processingthe waste material generated from the burning of coals containing highlevels of calcium oxide and transient metal such as iron, manganese,chromium, titanium or the like, e.g. up to 25% CaO and up to 24% Fe₂ O₃.

A further object of the invention includes a method of producing glassmaterials from ash-slag waste, having the following composition, wt %:

    ______________________________________                                        CaO total       5.0-41.0                                                      CaO unbound     4.0-13.0                                                      SiO.sub.2      13.0-75.0                                                      Al.sub.2 O.sub.3                                                                              5.0-26.0                                                      carbon         1.0-2.0                                                        Fe.sub.2 O.sub.3                                                                              1.0-24.0                                                      MgO            2.0-6.0                                                        Na.sub.2 O     0.1-1.0                                                        K.sub.2 O      0.2-1.0                                                        SO.sub.3       0.1-0.6                                                        TiO.sub.2      0.2                                                            ______________________________________                                    

The ash-slag waste is heated to a melting point temperature and meltedin a reducing medium, whereupon the melt obtained is cooled by a thermalshock, i.e. immersion in a cooling bath, preferably water, until afoamed glass material is formed. According to the invention, prior toheating the charge, the carbon content of the charge is brought to3.0-8.0 wt %, and the formation of the foamed glass material is carriedout in a flow of a gaseous medium. In one embodiment, where it isrequired to obtain a glass material with a maximum porosity adapted foruse as a heat-insulating material, the gaseous medium is derived fromgases resulting from decomposition of carbides in water which occursduring the thermal shock.

Alternatively, if it is necessary to obtain a glass material of aspherical shape which finds wide application in diverse branches ofindustry, for instance from chemical industry (as filters) to aircraftindustry (as a light heat-insulating material), the gaseous medium issupplemented by the addition of an inert gas fed to the melt.

It is possible that the gaseous medium is essentially a mixture of theadditionally fed inert gas and the gases resulting form decomposition ofcarbides in water. This will enable one to obtain glass materials fromash-slag waste with maximum porosity and low content of aluminum oxidesand calcium oxides.

For the manufacture of lime bricks, wall facing tiles used inconstruction industry, advantageously, the obtained glass material isadditionally disintegrated and press-molded with subsequent heating orroasting.

The obtained material may also be additionally heated to form a melt andthen slowly cooled. This helps obtain glass ceramic wear-resistantmaterials.

To produce optical materials with a wide transmissivity and a hightransparency in the visible and infrared spectra of electromagneticwaves, the foamed glass material obtained should be additionally heatedto form a melt and then cooled with subsequent heating or roasting.

BRIEF DESCRIPTION OF THE DRAWINGS

The sole FIGURE depicts a flow sheet of one mode of the inventivemethod.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention permits the utilization of coal ashes obtainedfrom the burning of brown coal or the like as a unique materialapplicable to construction projects and high performance ceramicglasses. The inventive method is particularly adapted to the treatmentof coal ashes containing considerable amounts of free calcium oxide andtransition metals such as iron, manganese, chromium, titanium or thelike.

By practicing the inventive method, ready-to-use products are providedsuch as:

Thermal insulation slabs for warmth-preserving layers in single blockhouse construction or as warmth-preserving means for roofs, floors andpanels;

Ceramic glass, tile for internal walls and floor lining;

Glass tile for internal wall lining and external wall facing;

Efficient brick with high performance characteristics for brick layingof external walls and storied buildings; and

Tiles for roofs of buildings.

Prior art building materials based on highly calcinized ashes from theburning of brown coal get destroyed within time due to the process ofhydration of the chemically uncombined calcium oxide present therein.The inventive method solves this problem by the formation of a foamedglass material using a thermal shock or cooling step wherein gases arereleased during the thermal shock to form a porous enclosed structure.

Exemplary properties of foamed material formed according to theinvention have the following characteristics:

Porosity: 10-80%;

Density: 50 to 300 kilogram/cubic meter;

Acid resistance to 96% sodium chloride solution: 99.07%;

Alkali resistance to 35% in a NaCl solution: 99.06%--thermalconductivity--0.04 to 0.08 watts/micron °C.

The obtained foamed glass materials can be used as original thermalinsulation material and as an accumulator during the production of lightconcrete and thermal insulation slabs. Formation of these slabs isconsidered to be well known in the art and further detail is not deemednecessary for understanding of the invention. These slabs, when usingnon-organic materials as a binder and a small amount of awater-repellant addition, exhibit the following physical-mechanicalcharacteristics:

Thermal conductivity: 0.025-0.65 watts/micron °C.;

Strength under compression 0.35-0.65 MPa, under curve 0.25-0.040 MPa;

Density: 250-350 Kilogram/cubic meters;

Water adsorption within one hour: 5-7% of slab mass.

As stated above, one of the problems involved in using coal ashes fromburned brown coal is the presence of transition metals in the brown coalash-slag waste. The inventive method overcomes this problem byadjustment of the carbon content of the ash-slag waste to a level whichpurifies the melt by reduction of transition metal oxides and generationof a gaseous medium to produce the foamed glass material.

The adjustment of the carbon content of the charge of ash-slag waste isdependent on the levels of carbon and transition metals in the waste.Since the ash-slag waste typically contains small levels of carbon, thecarbon content must be increased to an effective amount, preferably tobetween 3 and 8% weight of the charge for effective transition metalrecovery and formation of the gaseous material for foamed glass materialproduction. When adjusting the carbon content, it is preferred to addbrown coal to the ash-slag waste prior to melting. However, carbonbriquettes, graphite or the like may be used to adjust the carbon levelof the ash-slag waste prior to melting. The effective amount of carbonis that amount sufficient to reduce the iron levels to less than 0.15%iron and form carbides in sufficient quantity to form gases for theboiling layer effect.

Once the charge is adjusted in carbon, it is melted at which time thecarbon in the charge interacts with the transition metal oxides,particularly iron oxide, to form a separate melt of the transitionmetals which separates from the slag melt based upon the difference indensities. The iron oxides are reduced by the following equation:

    2Fe.sub.2 O.sub.3 +C→4Fe+3CO.sub.2 ↑

    2FeO+C→2Fe+CO.sub.2 ↑

During this step, the carbon also combines with calcium, aluminum andother alkaline or alkaline-earth metals in the melted material to formcarbides. These carbides as well as silicides and sulfides of the alkalior alkaline earth metals also interact with the iron oxide for ironrestoration. The free calcium oxide is tied up or bound by way of thefusion occurring during ash-slag melting.

The second step for restoring the iron involves the thermal shock stepwherein the melted ash-slag waste is charged into a cooling bath. Duringthis step, water-soluble carbides and sulfides present in the moltenash-slag waste combine with the cooling water to generate gases ofcarbon monoxide, carbon dioxide, hydrogen and water. This abundantrelease of gas creates a boiling layer effect which makes the moltenmaterial porous. The amount of gas generated is principally dependentupon the number of carbides formed in the melted ash-slag waste. Thegeneration of the gas can be calculated stoichiometrically based uponthe initial charge analysis, taking into account the carbon, iron, etc.Since this mass balance is well within the skill of the art, a furtherdetailed explanation is not deemed necessary.

The amount of gas produced as a result of the thermal shocking steprelates also to the structure of the foamed material. A more open ormore closed porous structure can be achieved depending on the volume ofgas. It is preferred that about 33 cubic centimeters of gas per 100grams of molten material is maintained for foaming the molten ash-slagwaste. A higher ratio of gas to molten material will result in a moreporous structure. Likewise, a lower ratio will result in a more closedstructure. A broad range for the gas to molten material ratio extendsbetween about 10 cubic centimeters per 100 grams of molten material upto several thousand centimeters of gas (3000) per 100 grams of moltenmaterial. The sole FIGURE details the processing steps described abovewherein the carbon content of the charge is adjusted and the meltedcharge is cooled by pouring it into a water bath to produce the foamedmaterial.

As stated, the restoration of iron is dependent on the chemicalcomposition of the ash-slag waste and also the temperature of the melt.Typically, the iron is reduced in stages. For example, a charge havingan iron oxide content ranges between 1 and 24 weight percent can bebrought down to as low as 0.01% by weight total iron using the inventiveprocess. The iron formed during melting can be separated from the moltenslag. Further iron formation can be recovered during the boiling layerphase of the method. Typically, more than 50% of the iron oxide isreduced during the thermal shock step. The minute amount of iron in thefoamed glass material makes it possible to use it as a source rawmaterial for crystal ceramic glass materials having a high coefficientof light absorption and light transmissivity.

It is also possible to form the foamed gas material of a spherical shapeby introducing an inert gas in addition to the gas generated from thedecomposition of the carbides formed in the molten ash-slag waste. Thisinert gas can be introduced by flowing it into the melt as it is pouredinto the cooling bath. Alternatively, the inert gas, preferably, carbondioxide, can be injected into the cooling bath while the melt is pouredtherein. The inert gas tends to break up the stream of molten materialinto separate portions which allows for better control of the geometricsizes of the foam materials. In addition, the inert gas serves as acover to protect the molten material from oxidation.

In another aspect of the invention, the foamed glass material can beused as a source material for the production of bricks and blocks with afiring and non-firing method. In these methods, the foamed material maybe ground to a suitable brick making size, e.g. <200 mesh. Morepreferably, the foamed material is reduced to <80μ.

The firing method includes molding a product out of the foamed material,drying and firing it at an elevated temperature as is commonly done inbrick manufacture. Exemplary of these temperatures include a range from900° to 1200° C. The maximum temperature for the firing is determined bythe maximum level of crystallization at the curve of the differentialthermal analysis.

During the press molding step, conventional binders such as soda glass,cement, tar, lignosulfinate etc. can be used during press molding.

Bricks made according to this method have the following characteristics:

Thermal conductivity in the dry state: 0.415±5.1% watts/micron °C.;

Compression limit: 30 MPa;

Water adsorption: 12 to 18%;

Frost resistance, frost-defrost cycles: 75.

These products are comparable with ceramic hollow brick for its thermalconductivity, compression resistance limits and can be used in thinnerfence constructions.

The non-firing method includes molding the products out of the foamedmaterial with a cementing material in the amount of about 20% of thetotal weight followed by natural drying for up to 20 days. The physicaland mechanical characteristics of these bricks are:

Thermal conductivity: 0.525 watts/microns °C.;

Compression limit: 30 MPa;

Water adsorption: 26%;

Frost resistance, frost-defrost cycle: more than 50.

The products according to the non-firing method correspond to the brickwith compression resistance limits of 30 MPa and relate to the group ofconventionally efficient bricks providing thermal-technicalcharacteristics for fences while using reduced brick thicknesses.

The firing method, also characterized as roasting, is carried out inatmospheric air and strengthens the foam glass material after it hasbeen molded or pressed into a desired shape. When the foamed glassmaterial is disintegrated, it can also be roasted in atmospheric air toincrease its rigidity for subsequent pressing or molding.

The pore size of the foamed glass material can vary depending on theprocessing parameters of the thermal shock and the nature of the moltenash-slag waste. The pore sizes can range from a few microns to severalmillimeters. One of the most important characteristics of the porousmaterial is the heat conductivity. The heat conductivity can fluctuatein the range of 0.04 to 0.09 watts per micron °C., depending on thechemical composition of the molten material in the size of the pores.

In yet a further aspect of the invention, optical materials with a widetransmissivity and high transparency for invisible and infrared spectracan be formed using the inventive foamed glass material. In this aspect,the foamed glass material obtained from the thermal shock step describedabove is melted and poured into molds which have been preheated to adesired temperature, e.g. 400°-600° C. The melted material in the moldsis maintained at a temperature, preferably 800° to 850° C. for one totwo hours followed by subsequent cooling to room temperature. With thissequence of steps, a glass ceramic material is produced having a highlight transmissivity. This high transmissivity is a result of thepurification step described above wherein the transition metals such asiron and the like are removed such that the foamed glass material is lowin iron content. This material can then be poured into molds and cooledto obtain a desired shape.

A more preferred method of producing glass materials from ash-slag wastecomprises providing a charge of the waste having the followingcomposition (wt %)

    ______________________________________                                        CaO total       5.0-41.0                                                      CaO unbound     4.0-13.0                                                      SiO.sub.2      13.0-75.0                                                      Al.sub.2 O.sub.3                                                                              5.0-26.0                                                      carbon         1.0-2.0                                                        Fe.sub.2 O.sub.3                                                                              1.0-24.0                                                      MgO            2.0-6.0                                                        Na.sub.2 O     0.1-1.0                                                        K.sub.2 O      0.2-1.0                                                        SO.sub.3       0.1-0.6                                                        TiO.sub.2      0.2,                                                           ______________________________________                                    

wherein the charge is heated to a melting point temperature and meltedin a reducing medium, whereupon the obtained melt is cooled by a thermalshock with simultaneous formation of the foamed glass material in theflow of gaseous medium.

In ash-slag waste formed as a result of burning coals of variousdeposits, carbon content generally does not exceed 5 wt % which is notsufficient for carrying out the process, permit complete recovery ofiron oxides and form carbides. Therefore, for carrying out the processof direct recovery of iron oxides, prior to heating of the charge, thecarbon content is brought to 3.0-8.0 wt %. This quantity range of thecarbon is dependent upon the percentage content of iron oxides in theinitial ash-slag waste material. The carbon is added in any conventionalmanner, preferably by the addition of coal to the waste prior tomelting.

The reducing medium can be any type known in the art such as CO, H₂,natural gas, producer gas or the like.

To prepare the glass material with the foamed structure, the processuses gases resulting from decomposition of carbides, inert gases or themixture of both.

Given below are specific examples of carrying out the method ofproducing glass materials from ash-slag waste formed by burning coals.Differences in the replaced percentages from 100% are based uponunanalyzed components and losses during testing.

EXAMPLE 1

500 g of ash-slag waste (ash) of the following composition (wt %):

    ______________________________________                                               CaO total                                                                              20.0                                                                 CaO unbound                                                                            4.0                                                                  SiO.sub.2                                                                              48.47                                                                Al.sub.2 O.sub.3                                                                       9.43                                                                 carbon   1.0                                                                  Fe.sub.2 O.sub.3                                                                       6.0                                                                  MgO      0.31                                                                 Na.sub.2 O                                                                             0.31                                                                 K.sub.2 O                                                                              0.36                                                                 SO.sub.3 0.13                                                                 TiO.sub.2                                                                              0.2,                                                          ______________________________________                                    

is melted in a graphite crucible at a temperature of from 1350 to 1550°C. for two hours and a half. Prior to heating, the carbon content in thecharge is brought to 3.0 wt %. The carbon reduces the iron to produce amelt with total iron content of 0.15 wt %. This melt is cooled under theconditions of thermal shock by pouring into water.

The thermal shock causes instantaneous foaming of the glass material.The obtained porous material is disintegrated to attain a requiredfineness and calcined to strengthen the pores by heating to 850° C. inair, and then cooled. The obtained glass material has a bulk density of150 kg/m³.

EXAMPLE 2

500 g of ash of the composition similar to that of Example 1 is meltedin a graphite crucible at a temperature of from 1350° to 1550° C. fortwo hours. The obtained melt having a total iron content of 0.1 wt % iscooled under the conditions of a thermal shock by pouring into water.This causes instantaneous foaming of the glass material. The obtainedporous glass material is disintegrated to attain a required fineness androasted by heating to a temperature of 850° C. to strengthen the pores,whereupon it is cooled. The material thus prepared has a bulk density of120 kg/m³.

EXAMPLE 3

500 g of ash of the composition similar to that of Example 1 is meltedin a graphite crucible at a temperature of 1350°-1550° C. for fourhours. The obtained melt having a total iron content of 0.05 wt % iscooled under the conditions of a thermal shock by pouring into water,whereby instantaneous foaming of the glass material takes place. Thefoamed glass material thus prepared is disintegrated to attain arequisite fineness and heated to 850° C. to strengthen the pores,whereupon it is cooled. The prepared glass material has a bulk densityof 80 kg/m³.

EXAMPLE 4

500 g of ash of the following composition (wt %):

    ______________________________________                                               CaO total                                                                              20.5                                                                 CaO unbound                                                                            11.7                                                                 SiO.sub.2                                                                              41.3                                                                 Al.sub.2 O.sub.3                                                                       5.0                                                                  carbon   3.0                                                                  Fe.sub.2 O.sub.3                                                                       12.0                                                                 MgO      4.5                                                                  Na.sub.2 O                                                                             1.2                                                                  K.sub.2 O                                                                              0.4                                                                  SO.sub.3 0.2                                                                  TiO.sub.2                                                                              0.2                                                           ______________________________________                                    

is heated and melted in a graphite crucible at a temperature of1350°-1550° C. for two hours and a half. Prior to heating of the charge,the carbon content therein is brought to 3 wt %. The melt thus obtainedhaving a total iron content of 0.15 wt % is cooled under the conditionsof a thermal shock by pouring into water. This causes instantaneousfoaming of the melt. The obtained porous glass material is disintegratedto attain a requisite fineness and heat-treated by the method depictedin Example 1. The prepared glass material features bulk density of 150kg/m³.

EXAMPLE 5

500 g of ash of the composition indicated in Example 4 is melted in agraphite crucible for three hours. The obtained melt with a total ironcontent of 0.1 wt % is cooled under the conditions of a thermal shock bypouring into water, whereby instantaneous foaming of the mass takesplace. The obtained porous glass material is heat-treated by the methodof Example 1. The prepared glass material features a bulk density of 100kg/m³.

EXAMPLE 6

500 g of ash of the composition described in Example 4 is melted forfour hours, the obtained melt with the iron content of 0.05 wt 8,chromium, 0.02 wt % and titanium, 0.1 wt %, is cooled in the similar wayas in Examples 4 and 5. The obtained glass material has a bulk densityof 50 kg/m³.

EXAMPLE 7

500 g of ash with the composition, wt %:

    ______________________________________                                        CaO total       3.1                                                           CaO unbound     none                                                          SiO.sub.2       50.5                                                          Al.sub.2 O.sub.3                                                                              19.2                                                          carbon          5.0                                                           Fe.sub.2 O.sub.3                                                                              20.0                                                          MgO             0.6                                                           Na.sub.2 O      0.2                                                           K.sub.2 O       0.9                                                           SO.sub.3        0.4                                                           TiO.sub.2       0.2                                                           ______________________________________                                    

Prior to heating the charge, the carbon content in the charge is broughtto 8 wt %, then the charge is melted in a graphite crucible at atemperature of 1350° to 1550° C. for two hours and a half. The melt thusproduced having a total iron content of 0.15 wt % is cooled under theconditions of a thermal shock by pouring into water.

This cause instantaneous foaming of the mass. The obtained porous glassmaterial is heat-treated similarly to Example 2. The glass materialproduced is characterized by a bulk density of 150 kg/m³.

EXAMPLE 8

500 g of ash having the composition listed in Example 7 is melted andheat-treated similarly to Example 2. The prepared glass material has abulk density of 120 kg/m₃.

EXAMPLE 9

500 g of ash of the composition indicated in Example 7 is melted andheat-treated similarly to the Example 3. The produced glass materialfeatures a bulk density of 80 kg/m³.

EXAMPLE 10

500 g of ash having the following composition (wt %):

    ______________________________________                                        CaO total       20.0                                                          CaO unbound     4.0                                                           SiO.sub.2       58                                                            Al.sub.2 O.sub.3                                                                              9.4                                                           Fe.sub.2 O.sub.3                                                                              1.0                                                           MgO             5.3                                                           Na.sub.2 O      0.3                                                           K.sub.2 O       0.4                                                           SO.sub.3        0.13                                                          TiO.sub.2       0.2                                                           ______________________________________                                    

wherein the carbon content in the charge is brought to 3 wt %, is heatedand melted in a graphite crucible at a temperature of 1350° to 1550° C.for an hour and a half. The obtained melt with a total iron contentamounting to 0.15 wt % is cooled under the conditions of a thermal shockby pouring into water, whereby instantaneous foaming of the glassmaterial is caused. The obtained porous glass material is disintegratedto attain a requisite fineness and roasted to a temperature of 850° C.,and subsequently cooled. The prepared glass material has a bulk densityof 150 kg/m³.

EXAMPLE 11

500 g of ash of the composition specified in Example 10 is melted in agraphite crucible at a temperature of 1340°-1550° C. for two hours. Themelt obtained with a total iron content of 0.1 wt % is cooled under theconditions of a thermal shock by pouring into water, wherebyinstantaneous foaming of the material is caused. The obtained porousglass material is processed similarly to Example 10. The prepared glassmaterial is characterized by a bulk density of 120 kg/m³.

EXAMPLE 12

500 g of ash having the composition of Example 10 is melted in agraphite crucible at a temperature of 1350°-1550° C. for two hours and ahalf. The melt thus prepared with a total iron content of 0.05 wt % iscooled under the conditions of a thermal shock by pouring into water.This causes instantaneous foaming of the glass material. The obtainedglass material is processed as in Example 10. The density of the glassmaterial is 80 kg/m³.

EXAMPLE 13

500 g of ash having the composition specified in Example 1 is melted andheat treated in the way similar to that of Example 1. The obtained glassmaterial is dispersed to the fineness sized from 0 to 80 μm, then cubesof 100×100×100 mm size and bars of 40×40×100 mm size are press moldedfrom the powder. The molded articles are dried and roasted at atemperature of 950° C. for 50 min with subsequent cooling in thefurnace. The produced samples have the following characteristics:

    ______________________________________                                        ultimate compression strength, MPa                                                                   39.3                                                   ultimate bending strength, MPa                                                                       7.7                                                    ______________________________________                                    

EXAMPLE 14

500 g of ash of the composition indicated in Example 1 is melted andheat-treated as in Example 2. The obtained glass material is dispersedto the fineness of from 0 to 80 μm, then cubes of 100×100×100 mm sizeand bars of 40×40×160 mm size are press-molded from the powder. Themolded articles are dried and then roasted at a temperature of 950° C.for 30 min with subsequent cooling in the furnace. The obtained sampleshave the following characteristics:

    ______________________________________                                        ultimate compression strength, MPa                                                                   40.0                                                   ultimate bending strength, MPa                                                                       8.0                                                    ______________________________________                                    

EXAMPLE 15

500 g of ash of the composition indicated in the Example 1 is melted andheat treated similarly to Example 3. The obtained glass material isdispersed to the fineness of from 0 to 80 μm, then molded and heattreated as in Example 10. The obtained samples feature the followingcharacteristics:

    ______________________________________                                        ultimate compression strength, MPa                                                                   43.2                                                   ultimate bending strength, MPa                                                                       8.1                                                    ______________________________________                                    

EXAMPLE 16

500 g of ash having the composition specified in Example 4 is melted andheat treated in the way similar to that of Example 1, the articles aremolded and roasted as in Example 13. The obtained samples have thefollowing characteristics:

    ______________________________________                                        ultimate compression strength, MPa                                                                   39.0                                                   ultimate bending strength, MPa                                                                       7.5                                                    ______________________________________                                    

EXAMPLE 17

500 g of ash having the composition similar to that of Example 4 ismelted and heat treated as in Example 2. Then the material is dispersed,molded and heat treated in the same manner as in Example 13. Theobtained samples have the following characteristics:

    ______________________________________                                        ultimate compression strength, MPa                                                                   43.0                                                   ultimate bending strength, MPa                                                                       8.3                                                    ______________________________________                                    

EXAMPLE 18

500 g of ash having the composition indicated in Example 4 is melted,heat treated, molded and roasted in the similar way as in Examples 3 and13. The obtained samples have the following characteristics:

    ______________________________________                                        ultimate compression strength, MPa                                                                   44.2                                                   ultimate bending strength, MPa                                                                       8.5                                                    ______________________________________                                    

EXAMPLE 19

500 g of ash having the composition indicated in Example 7 is melted,heat treated and roasted similarly to Examples 1 and 13. The obtainedsamples have the following characteristics:

    ______________________________________                                        ultimate compression strength, MPa                                                                   19.1                                                   ultimate bending strength, MPa                                                                       2.6                                                    ______________________________________                                    

EXAMPLE 20

500 g of ash of the composition specified in Example 7 is melted, heattreated, molded and roasted similarly to Examples 2 and 13. The obtainedsamples have the following characteristics:

    ______________________________________                                        ultimate compression strength, MPa                                                                   19.5                                                   ultimate bending strength, MPa                                                                       2.7                                                    ______________________________________                                    

EXAMPLE 21

500 g of ash having the composition specified in Example 7 is melted,heat treated, molded and roasted in the way similar to that of Examples3 and 13.

The obtained samples have the following properties:

    ______________________________________                                        ultimate compression strength, MPa                                                                   20.0                                                   ultimate bending strength, MPa                                                                       2.6                                                    ______________________________________                                    

EXAMPLE 22

500 g of ash having the composition similar to that of Example 7 ismelted, heat treated and molded as in Example 3 and 13, while roastingis carried out at a temperature of 1050° C. for thirty minutes withsubsequent cooling in the furnace. The obtained samples have thefollowing characteristics:

    ______________________________________                                        ultimate compression strength, MPa                                                                   60.0                                                   ultimate bending strength, MPa                                                                       9.0                                                    ______________________________________                                    

EXAMPLE 23

500 g of ash of the composition of Example 1 is melted in a graphitecrucible at a temperature of from 1350° to 1450° C. for two hours and ahalf. The obtained melt having a total iron content of 0.15 wt % ispoured into graphite molds preheated to 550° C., then the temperature israised to 800°-850° C., the melt stands at this temperature for an hourand a half with subsequent cooling in the electric furnace to a roomtemperature. The prepared glass ceramic materials have the followingcharacteristics:

    ______________________________________                                        light transmission factor, %                                                                         30.0                                                   thermal conductivity, W/m · K micron                                                         0.8                                                   linear expansion coefficient °C..sup.-1                                                       6 × 10.sup.-6                                    ultimate bending strength, MPa                                                                       75.0                                                   ______________________________________                                    

EXAMPLE 24

500 g of ash having the composition specified in Example 1 is melted asin Example 2. The obtained melt is poured into the mold and heat treatedin the way similar to that of Example 23. The prepared glass ceramicmaterials have the following properties:

    ______________________________________                                        light transmission factor, %                                                                         40.0                                                   thermal conductivity, W/m · K                                                                0.8                                                   linear expansion coefficient, °C..sup.-1                                                      5 × 10.sup.-6                                    ultimate bending strength, MPa                                                                       75.0                                                   ______________________________________                                    

EXAMPLE 25

500 g of ash having the composition indicated in Example 1 is melted inthe way similar to that of Example 3, molded and roasted as in Example23. The produced glass ceramic materials have the followingcharacteristics:

    ______________________________________                                        light transmission factor, %                                                                         50.0                                                   thermal conductivity, W/m · K                                                                0.7                                                   linear expansion coefficient, °C..sup.-1                                                      5 × 10.sup.-6                                    ultimate bending strength, MPa                                                                       80.0                                                   ______________________________________                                    

EXAMPLE 26

500 g of ash of the composition specified in Example 4 is processed asdisclosed in Example 23. The glass ceramic materials produced have thefollowing properties:

    ______________________________________                                        light transmission factor, %                                                                         30.0                                                   thermal conductivity, W/m · K                                                                0.8                                                   linear expansion coefficient, °C..sup.-1                                                      6 × 10.sup.-6                                    ultimate bending strength, MPa                                                                       75.0                                                   ______________________________________                                    

EXAMPLE 27

500 g ash having the composition specified in Example 4 is processed asin Example 24. The obtained glass ceramic materials have the followingcharacteristics:

    ______________________________________                                        light transmission factor, %                                                                         40.0                                                   thermal conductivity, W/m · K                                                                0.75                                                  linear expansion coefficient, °C..sup.-1                                                      5.5 × 10.sup.-6                                  ultimate bending strength, MPa                                                                       75.0                                                   ______________________________________                                    

EXAMPLE 28

500 g of ash with the composition of Example 4 is processed in the waysimilar to Example 25. The obtained glass ceramic materials have thefollowing properties:

    ______________________________________                                        light transmission factor, %                                                                         50.0                                                   thermal conductivity, W/m · K                                                                0.7                                                   linear expansion coefficient, °C..sup.-1                                                      5 × 10.sup.-6                                    ultimate bending strength, MPa                                                                       80.0                                                   ______________________________________                                    

EXAMPLE 29

500 g of ash having the composition indicated in Example 7 is heattreated in the way similar to that of Example 23.

The produced glass ceramic materials feature the followingcharacteristics:

    ______________________________________                                        light transmission factor, %                                                                         30.0                                                   thermal conductivity, W/m · K                                                                0.8                                                   linear expansion coefficient, °C..sup.-1                                                      5 × 10.sup.-6                                    ultimate bending strength, MPa                                                                       90.0                                                   ______________________________________                                    

EXAMPLE 30

500 g of ash of the composition indicated in Example 7 is heat treatedas in Example 24. The obtained glass ceramic materials have thefollowing characteristics:

    ______________________________________                                        light transmission factor, %                                                                         40.0                                                   thermal conductivity, W/m · K                                                                0.75                                                  linear expansion coefficient, °C..sup.-1                                                      5 × 10.sup.-6                                    ultimate bending strength, MPa                                                                       95.0                                                   ______________________________________                                    

EXAMPLE 31

500 g of ash having the composition indicated in Example 7 is heattreated in the way similar to that of Example 25. The glass ceramicmaterials produced have the following characteristics:

    ______________________________________                                        light transmission factor, %                                                                         50.0                                                   thermal conductivity, W/m · K                                                                0.7                                                   linear expansion coefficient, °C..sup.-1                                                      5 × 10.sup.-6                                    ultimate bending strength, MPa                                                                       100                                                    ______________________________________                                    

EXAMPLE 32

500 g of the porous glass material obtained in Example 1 is placed intoan alundum crucible and melted at a temperature of from 1450° to 1500°C. for 2 hours. The melt is poured into graphite molds which have beenpreheated to 550° C. and heated to 850° C., whereupon the melt stands atthis temperature for two hours with subsequent cooling in the furnace toa room temperature.

The transmissivity in the visible and infrared spectra ofelectromagnetic waves of the samples is equal to 75%.

EXAMPLE 33

500 g of the porous glass material obtained in Example 2 is melted andheat treated similarly to the process of Example 32. The transmissivityin the visible and infrared spectra of electromagnetic waves of theobtained samples is 85%.

EXAMPLE 34

500 g of the porous glass material obtained in Example 3 is melted andheat treated similarly to the process of Example 32. The transmissivityin the visible and infrared spectra of electromagnetic waves of thesamples produced amounts to 95%.

EXAMPLE 35

500 g of the porous glass material obtained in Example 4 is melted andheat treated as in Example 32. The transmissivity in the visible andinfrared spectra of electromagnetic waves of the samples produced is70%.

EXAMPLE 36

500 g of porous glass material prepared in Example 5 is melted and heattreated as in Example 32. The transmissivity in the visible and infraredspectra of electromagnetic waves is 80%.

EXAMPLE 37

500 g of porous glass material obtained in Example 6 is melted and heattreated similarly to the process of Example 32. The transmissivity inthe visible and infrared spectra of electromagnetic waves of the samplesproduced amounts to 90%.

EXAMPLE 38

500 g of porous glass material obtained in Example 7 is melted and heattreated as in Example 32. The transmissivity in the visible and infraredspectra of electromagnetic waves of the samples produced is 70%.

EXAMPLE 39

500 g of porous material obtained in Example 8 is melted and heattreated as in Example 32. The transmissivity in the visible and infraredspectra of electromagnetic waves of the glass ceramic material obtainedis 80%.

EXAMPLE 40

500 g of porous material obtained in Example 9 is melted and heattreated similarly to the process of Example 29. The transmissivity inthe visible and infrared spectra of electromagnetic waves of the glassceramic materials produced amounts to 95%.

EXAMPLE 41

500 g of ash having the composition specified in Example 4 is melted asin Example 4. The obtained melt is cooled under the conditions of athermal shock by pouring it onto an flow of inert gas (CO₂) ascending inthe direction of pouring.

This result in that the obtained glass material acquires a hollowspherical shape with the density of its granules amounting to 1000kg/m³.

EXAMPLE 42

500 g of ash formed having the composition indicated in Example 4 ismelted as described above. The obtained melt cooled under the conditionsfor a thermal shock by pouring into water, accompanied by blowing inertgas (CO₂) into the water, whereby more than 50% of the glass materialhas a hollow spherical shape of various diameters with the granulesdensity of 500 kg/m³.

EXAMPLE 43

500 g of ash having the composition specified in Example 4 is melted asin Example 4. The obtained melt is cooled under the conditions of athermal shock by pouring the melt into water through the foamedmaterial. Consequently, less than 50% of the total mass of the glassmaterial produced has a hollow spherical shape of different diameterswith the density of the granules from 100 to 300 kg/m³.

Industrial Applicability

The present invention can be most effectively used for the production ofconstruction materials of diverse purposes (bricks, heat- andsound-insulating materials, facing and ceramic materials) filteringmaterials, chemically stable materials. Moreover, the proposed methodhelps obtain glass materials featuring a high light transmission factorand utilized in magnetooptics (magnetooptical memory disks, liquidcrystal light modulators), as well as in astronomical optics.

We claim:
 1. A method of producing foamed glass materials from ash-slagwaste derived from burning coals comprising the steps of:a) providing acharge of the ash-slag waste including calcium oxide and iron oxide inthe following amounts of wt %:

    ______________________________________                                        CaO total      5.0-41.0                                                       CaO unbound    4.0-13.0                                                       Fe.sub.2 O.sub.3                                                                             1.0-24.0                                                       ______________________________________                                    

b) heating and melting the charge; and c) forming said foamed glassmaterial by pouring said melted charge into a water bath; d) wherein,prior to said heating and melting of the charge, a carbon content of thecharge is adjusted to an amount effective to reduce the Fe₂ O₃ contentof the charge to less than 1% by weight and to form carbides in saidmelt whereby a gaseous medium is generated from the carbides to foamsaid melt to produce the foamed glass materials.
 2. A method accordingto claim 1, wherein said adjusting step comprises adjusting the carboncontent of the charge to 3.0 to 8.0 wt % carbon.
 3. A method accordingto claim 1, wherein said melt is contacted with an inert gas.
 4. Amethod according to claim 3, comprising blowing the inert gas into thewater bath.
 5. The method of claim 3 wherein the inert gas is injectedinto said melt during the pouring of said melt into said water bath. 6.The method of claim 1 further comprising the steps of disintegratingsaid foamed glass material, heating said disintegrated glass material inair to increase its strength and cooling said heated glass material toincrease the bulk density of said glass material.
 7. The method of claim1 further comprising the steps of disintegrating said foamed glassmaterial, press molding said disintegrated glass material to apredetermined shape, heating said press molded glass material in air toincrease its strength and cooling said heated glass material to form amolded article.
 8. The method of claim 1 further comprising the step ofmelting said foamed glass materials, heating said melted glass materialand cooling said heated material to form an optical material.
 9. Themethod of claim 1 wherein said gaseous medium is generated at a ratebetween 10 and 3000 cubic centimeters/100 gm of said charge.
 10. Themethod of claim 9 wherein said rate ranges between 30 and 90 cubiccentimeters/100 gm of said charge.
 11. The method of claim 1 wherein thecharge of the providing step has the following composition:

    ______________________________________                                        CaO total       5.0-41.0                                                      CaO unbound     4.0-13.0                                                      SiO.sub.2      13.0-75.0                                                      Al.sub.2 O.sub.3                                                                              5.0-26.0                                                      carbon         1.0-2.0                                                        Fe.sub.2 O.sub.3                                                                              1.0-24.0                                                      MgO            2.0-6.0                                                        Na.sub.2 O     0.1-1.0                                                        K.sub.2 O      0.2-1.0                                                        SO.sub.3       0.1-0.6                                                        TiO.sub.2      0.2, and                                                       ______________________________________                                    

the adjusted carbon of the charge ranges between 3.0 and 8.0 wt %.